Ion implantation is a standard technique for introducing conductivity-altering impurities into a workpiece. A desired impurity material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the ion beam penetrate into the bulk of the workpiece material and are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity.
Two concerns of the solar cell manufacturing industry are manufacturing throughput and cell efficiency. Cell efficiency measures the amount of energy converted into electricity. Higher cell efficiencies may be needed to stay competitive. However, manufacturing throughput likely cannot be sacrificed at the expense of increased cell efficiency.
Ion implantation has been demonstrated as a viable method to dope solar cells. Use of ion implantation removes process steps needed for existing technology, such as diffusion furnaces, which increases throughput and may lower costs. For example, a laser edge isolation step may be removed if ion implantation is used instead of furnace diffusion because ion implantation will only dope the desired surface. Besides removal of process steps, higher cell efficiencies have been demonstrated using ion implantation. Ion implantation also offers the ability to perform a blanket implant of an entire surface of a solar cell or a selective (or patterned) implant of only part of the solar cell. Selective implantation at high throughputs using ion implantation avoids the costly and time-consuming lithography or patterning steps used for furnace diffusion. Any improvement to manufacturing throughput of an ion implanter or its reliability would be beneficial to solar cell manufacturers worldwide. This may accelerate the adoption of solar cells as an alternative energy source.